diff --git a/include/ntapi/nt_process.h b/include/ntapi/nt_process.h
index f4f4aea..5a77ae9 100644
--- a/include/ntapi/nt_process.h
+++ b/include/ntapi/nt_process.h
@@ -577,7 +577,7 @@ typedef struct _nt_runtime_data {
 	uint32_t	reserved;
 
 	int32_t		umask;
-	int32_t		amask;
+	uint32_t	amask;
 
 	void *		hstdin;
 	void *		hstdout;